# $B_{s1}(5778)$ as a $B^*\bar{K}$ molecule in the Bethe-Salpeter equation approach

## TL;DR

This paper models the $B_{s1}(5778)$ as a molecular state of $B^*$ and $ar{K}$ using the Bethe-Salpeter equation, predicting bound states and decay properties relevant for future experiments.

## Contribution

It introduces a Bethe-Salpeter equation approach with various form factors to interpret $B_{s1}(5778)$ as a molecular state and calculates its decay widths.

## Key findings

- Bound state of $B^*ar{K}$ exists under the model.
- Decay widths for multiple decay channels are predicted.
- Results support the molecular interpretation of $B_{s1}(5778)$.

## Abstract

We interpret the $B_{s1}(5778)$ as an $S$-wave $B^\ast\bar{K}$ molecular state in the Bethe-Salpeter equation approach. In the ladder and instantaneous approximations, and with the kernel containing one-particle-exchange diagrams and introducing three different form factors (monopole, dipole, and exponential form factors) in the vertex, we find the bound state exists. We also study the decay widths of the decay $B_{s1}(5778)\rightarrow B_s^\ast\pi$ and the radiative decays $B_{s1}(5778)\rightarrow B_s\gamma$ and $B_{s1}(5778)\rightarrow B_s^{\ast}\gamma$, which will be instructive for the forthcoming experiments.